In the last few years it has become increasingly common for a hand-held wireless terminal (e.g., a supermarket scanner, a warehouse data-entry device, etc.) to be equipped with a wireless telecommunications capability to enable the wireless terminal to transmit information to a host system, or to receive information from the host system, or both. For example, a worker in a warehouse can carry a wireless terminal to assist a host system in monitoring inventory. The host system can transmit by radio to the wireless terminal a request to the worker to check how many units of a particular item are in the warehouse. After the worker has counted the number of units the worker can enter the number into the wireless terminal, which relays the number back to the host system by radio.
Although some wireless terminals (e.g., cellular telephones, cordless telephones, etc.) are manufactured with a permanent, integrated radio, other wireless terminals (e.g., hand-held data-entry devices, notebook computers, etc.) are not. One advantage of manufacturing a wireless terminal without a permanent radio is that it enables the end-user to select a radio for mating with the wireless terminal that is appropriate for the environment in which the wireless terminal is to operate.
The wireless terminals that are manufactured without an integrated radio are, however, usually manufactured with the capability to connect with a radio. Typically, the connection is made through an industry-standard interface that prescribes both the mechanical and electrical interface. Currently, the PCMCIA “PC Card” interface is the standard to which almost all wireless terminals are designed.
The PCMCIA interface prescribes a slot in the wireless terminal for receiving a credit-card shaped radio card and a 68-pin electrical connector on both the radio card and in the slot so that the radio card and the wireless terminal can share power, ground and signaling. The PCMCIA interface also specifies the voltages, timing, and signaling protocols on each lead of the 68-pin electrical connector.
Typically, a PCMCIA radio card has a built-in antenna for transmitting and receiving signals, but such a built-in antenna rarely has as good radio propagation characteristics as does an external antenna that is mounted on the outside of the wireless terminal. Therefore, when a user desires to have a PCMCIA radio card employ an external antenna that is part of the wireless terminal some provision must be made to electrically connect the radio card to the antenna. Unfortunately, the PCMCIA interface specification does not provide for the transmission of RF signals over the 68-pin interface, and, therefore, a separate cable must be provided to carry the RF signals between the antenna and a non-standard connector that must be added to the radio card.
It is also advantageous for a wireless terminal to display to the user the status of the radio. For example, a wireless terminal can have one LED that is illuminated when the radio is transmitting and another LED that is illuminated when the radio is receiving. When neither LED is illuminated, it means that the radio is in standby mode. When the radio is manufactured as a integral part of the wireless terminal, signals from the radio can control the illumination of the radio status LEDs through as many wires as are necessary.
In contrast, when the radio is contained in a PCMCIA radio card the radio has no inherent means for controlling the radio status LEDs because the PCMCIA interface specification does not provide for the transmission of radio status signaling. Therefore, a separate cable must be provided from a non-standard connector that must be added to the radio card to the LEDs so that the radio can control the illumination of the radio status LEDs.
It is clearly advantageous for a radio on a radio card to be able to use an external antenna that is mounted on the wireless terminal, but the necessity of providing a separate cable to carry the RF signals and a separate cable to carry the radio status LED control signals adds to the cost of both the wireless terminal and the radio card. Furthermore, each of the two cables must be connected to the radio card each time the radio card is inserted, which given that the components are small and the space constraints tight, can hamper the task of attaching the cables to the radio card. Therefore, a need exists for a better mechanism for connecting a radio on a radio card to an externally mounted antenna and a radio status display.